A statement said such behaviour would be "in complete contravention of the Civil Service Code".

It added there was no reason to suspect a "particular department" was involved.

'Exhausting every option'

The Cabinet Office statement said an investigation, led by Permanent Secretary Richard Heaton, had begun.

It said "important stakeholders" including the Hillsborough Family Support Group, the Hillsborough Justice Campaign and the All Party Parliamentary Group on the Hillsborough Disaster would be kept updated of developments.

How the source was uncovered

Wikipedia allows any web user to make changes to its pages, but this leaves a trace through the user's internet protocol (IP) address

Changes are monitored by Wikipedia, but internet trolls have been known to post insulting material, which is usually swiftly removed

Liverpool Echo reporter Oliver Duggan discovered that insults posted on the website's Hillsborough Disaster page had been made using computers within the government's internal intranet

He confirmed this after referring to a list of 34 IP addresses used by the government released by former minister Angela Eagle in 2008

It states: "The amendments made to Wikipedia are sickening. The behaviour is in complete contravention of the Civil Service Code. It is entirely unacceptable.

"At this time, we have no reason to suspect that the Hillsborough edits involve any particular department, nor more than one or two individuals in 2009 and 2012.

"As the first incident happened five years ago and there are hundreds of thousands of people on the government's network, it may prove challenging to identify who was involved, but we are exhausting every option."

The spokesman said that Andy Burnham MP, who "has a deserved status as an expert on the disaster", would be given the chance to "view all relevant material from the very outset so that he can assure himself all steps have been taken".

Mr Burnham said it was "sickening and appalling to think that people in government are aiming this kind of abuse at the Liverpool supporters - particularly the victims and survivors of that tragedy".

He said that "a full and proper inquiry [to] find the name of the individual or individuals responsible" needed to happen, adding that they must then be "held accountable - nothing else will do".

While Secretary for Culture, Media and Sport, Mr Burnham was instrumental in a campaign to have classified documents about the disaster released, which led to the formation of the Hillsborough Independent Panel.

Oliver Duggan, the Liverpool Echo reporter who broke the story, said the paper used a list of 34 IP addresses for Whitehall computers, released in 2008 by Angela Eagle MP following a parliamentary question to "match up" the addresses with those used to edit the Wikipedia page about the disaster.

The newspaper said the alterations to the page included the Liverpool anthem You'll Never Walk Alone being altered to You'll Never Walk Again and the phrase "Blame Liverpool Fans" being added to a paragraph.

Image copyrightWikipediaImage caption
A Wikipedia edit on the 20th anniversary of the disaster added the words 'Blame Liverpool Fans'

'Appalled by vandalism'

Steve Rotheram, the MP for Liverpool Walton, echoed Mr Burnham's remarks and said he and a group of Merseyside MPs would be writing to the government to ask that any inquiry "be swift".

"It's complex in its nature, but they need to put the resources in to find out who this individual or individuals are."

Sheila Coleman, spokeswoman for the Hillsborough Justice Campaign, said the group would be talking to its legal team about "how to proceed".

Ms Eagle, the MP for Wallasey, said the claims were "pretty shocking" and were "another problem for [the families] having to deal with the grief".

Entries in Wikipedia, an online encyclopaedia, can be edited by anyone with access to the internet.

Jon Davies, chief executive of Wikimedia UK, said it was "appalled by such vandalism".

Ninety-six Liverpool football fans died after a crush at an FA Cup semi-final at the Sheffield ground on 15 April 1989.

New inquests, which are ongoing, were ordered after new evidence revealed by the Hillsborough Independent Panel led to the original inquest verdicts being quashed.